Alopecia (baldness) is a deficiency of hair, either normal or abnormal, and is primarily a cosmetic problem in humans, although the negative psychological impact of hair loss is well known. See C. H. Mortimer et al., Clin. Exp. Dermatol. 9, 342-350 (1984). Dermatologists recognize many different types of alopecia, with androgenic alopecia being the most common cause of hair loss in both men and women. As this type of hair loss is more common and more severe in males, it is typically referred to as "male pattern baldness." However, it is thought that androgenic alopecia affects more that one third of individuals of either sex who have a strong family history of hair loss. See W. F. Bergfield, Clin. Dermatol. 6, 102-107 (1988).
One traditional treatment for alopecia is the method of hair transplantation. Typically, this method involves transplanting plugs of natural hair from areas of the scalp where hair is growing to bald areas. This procedure is costly, time-consuming, painful, and meets with only limited success.
Another common treatment for hair loss is the application of a chemical or drug for the purpose of stimulating hair growth. For example, U.S. Pat. No. 5,177,061 to Pickart proposes the topical application of glycyl-L-histidyl-L-lycine:copper(II) (GHL-Cu) and its derivatives to promote hair growth in warm-blooded animals (applicant specifically intends the disclosure of this and all other patent references cited herein to be incorporated herein by reference in their entirety). U.S. Pat. No. 4,832,946 to Green proposes a composition for topical application to mammalian hair or skin, comprising an amount of the cell-free supernatant from a culture of dermal papilla fibroblasts, which is said to increase hair growth in the rat. U.S. Pat. No. 5,358,714 to Green proposes the use of diacylglycerol activators of protein kinase C in order to increase or maintain hair growth in mammals, while U.S. Pat. No. 5,068,315 to Buultjens et al. proposes the application of purified hair growth regulating peptides (HGRP) to stimulate hair growth. It has also been suggested that retinoids, substituted pyrimidines, and immunosuppressants be used as possible treatments for hair loss, although methods utilizing these compounds have not been entirely successful in producing a reliable and safe method of inducing hair growth. See G. Bazzano et al., J. Invest. Dermatol. 101 (1 Supplement), 138S-142S (1993); H. Jiang et al., J. Invest. Dermatol. 104(4) , 523-525 (1995).
In recent years, the topical application of minoxidil has been a widely-used method for treating androgenic alopecia. See A. R. Zapacosta, N. Eng. J. Med. 303, 1480-81 (1980). U.S. Pat. No. 4,139,619 to Chidsey, proposes a topical composition of minoxidil and related iminopyrimidines to stimulate the conversion of vellus hair to terminal hair and increase the rate of growth of terminal hair. However, despite its popularity, minoxidil has not performed in a completely satisfactory fashion in promoting hair growth in all target populations.